We propose to study the alterations in free fatty acid and glucose utilization occurring with beta-blocker therapy in order to identify a potential mechanism for the improved prognosis occurring with third generation beta-blocker therapy in patients with heart failure. The purpose of this study is to non-invasively assess alterations in myocardial metabolism prior to and following three months of treatment with carvedilol in patients with cardiomyopathy using positron emission tomography (PET) and the PET perfusion tracers F-fluorodeoxyglucose (FDG) and F-fluoro-heptadecanoic acid (FTHA). We hypothesize that a shin in myocardial metabolism from primarily free fatty acid oxidation to enhanced glucose metabolism will occur following therapy with carvedilol in patients with cardiomyopathy. Enhanced FDG uptake reflective of increased glucose metabolism and depressed FTHA uptake reflective of decreased fatty acid metabolism following treatment with carvedilol would support the hypothesis that substrate-specific alterations occur in myocardial metabolism following treatment in patients with cardiomyopathy"